:root {
    --brand-primary: #00D4FF;
    --brand-secondary: #101626;
    --brand-accent: #34D399;
    --bg: #f4f7f6;
    --surface: #ffffff;
    --text: #333333;
    --text-muted: #666666;
    --border-color: #ddd;
    --shadow-light: rgba(0, 0, 0, 0.05);
    --shadow-medium: rgba(0, 0, 0, 0.08);
    --shadow-strong: rgba(0, 0, 0, 0.2);
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --border-radius-sm: 8px;
    --border-radius-md: 10px;
    --border-radius-lg: 12px;
}

body {
    font-family: system-ui, -apple-system, 'Segoe UI', sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

header {
    background-color: var(--brand-secondary);
    color: #ffffff;
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 4px var(--shadow-light);
}

header .logo {
    display: flex;
    align-items: center;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--brand-primary);
}

header .logo img {
    height: 40px;
    margin-right: 10px;
}

nav {
    display: flex;
    gap: var(--spacing-md);
}

nav a {
    color: #ffffff;
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: background-color 0.3s ease, color 0.3s ease;
}

nav a:hover,
nav a.active {
    background-color: var(--brand-primary);
    color: var(--brand-secondary);
}

.container {
    max-width: 1200px;
    margin: var(--spacing-lg) auto;
    padding: 0 var(--spacing-lg);
}

.page-section {
    display: none;
    background-color: var(--surface);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: 0 4px 12px var(--shadow-medium);
    margin-bottom: var(--spacing-lg);
}

.page-section h2 {
    color: var(--brand-primary);
    margin-bottom: var(--spacing-md);
    border-bottom: 2px solid var(--brand-primary);
    padding-bottom: var(--spacing-xs);
}

.card {
    background-color: var(--surface);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-md);
    box-shadow: 0 2px 8px var(--shadow-light);
    margin-bottom: var(--spacing-sm);
    border: 1px solid var(--brand-secondary);
}

.card h3 {
    color: var(--brand-secondary);
    margin-top: 0;
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
}

.form-group {
    margin-bottom: var(--spacing-sm);
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
    color: var(--text-muted);
}

.form-group input[type="text"],
.form-group input[type="email"],
.form-group input[type="number"],
.form-group input[type="date"],
.form-group select,
.form-group textarea {
    width: calc(100% - 20px);
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    border-color: var(--brand-primary);
    outline: none;
}

button {
    background-color: var(--brand-primary);
    color: var(--brand-secondary);
    border: none;
    padding: 12px 20px;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

button:hover {
    background-color: color-mix(in srgb, var(--brand-primary) 90%, black); /* Slightly darker primary */
    transform: translateY(-2px);
}

button.secondary {
    background-color: var(--brand-secondary);
    color: #ffffff;
}

button.secondary:hover {
    background-color: color-mix(in srgb, var(--brand-secondary) 90%, black); /* Slightly darker secondary */
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: var(--spacing-sm);
}

table th,
table td {
    border: 1px solid var(--border-color);
    padding: 12px;
    text-align: left;
}

table th {
    background-color: var(--brand-secondary);
    color: #ffffff;
    font-weight: 600;
}

table tr:nth-child(even) {
    background-color: color-mix(in srgb, var(--bg) 50%, white);
}

table tr:hover {
    background-color: color-mix(in srgb, var(--bg) 70%, white);
}

.alert {
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    margin-bottom: var(--spacing-sm);
    font-weight: 500;
}

.alert-success {
    background-color: color-mix(in srgb, var(--brand-accent) 20%, white);
    color: color-mix(in srgb, var(--brand-accent) 80%, black);
    border: 1px solid color-mix(in srgb, var(--brand-accent) 50%, white);
}

.alert-error {
    background-color: #f8d7da; /* Red-ish for error */
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.badge {
    background-color: var(--brand-accent);
    color: #ffffff;
    padding: 0.3rem 0.6rem;
    border-radius: 50%;
    font-size: 0.8rem;
    font-weight: 600;
    margin-left: 5px;
}

.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.4);
    justify-content: center;
    align-items: center;
}

.modal-content {
    background-color: var(--surface);
    margin: auto;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    width: 90%;
    max-width: 500px;
    box-shadow: 0 8px 25px var(--shadow-strong);
    position: relative;
}

.close-button {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
    position: absolute;
    top: 10px;
    right: 20px;
}

.close-button:hover,
.close-button:focus {
    color: var(--brand-primary);
    text-decoration: none;
    cursor: pointer;
}

#announcements .announcement-item {
    background-color: color-mix(in srgb, var(--surface) 95%, var(--bg));
    border: 1px solid #eee;
    padding: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    border-left: 5px solid var(--brand-accent);
    border-radius: var(--border-radius-sm);
}

#announcements .announcement-item h3 {
    color: var(--brand-secondary);
    margin-top: 0;
    margin-bottom: var(--spacing-xs);
}

#announcements .announcement-item p {
    margin-bottom: 0;
}

#announcements .announcement-item .date {
    font-size: 0.9em;
    color: var(--text-muted);
    text-align: right;
}

.timetable-day {
    margin-bottom: var(--spacing-md);
}

.timetable-day h3 {
    background-color: var(--brand-primary);
    color: var(--brand-secondary);
    padding: 0.8rem 1.2rem;
    border-radius: var(--border-radius-sm);
    margin-top: 0;
}

.timetable-entry {
    display: flex;
    background-color: color-mix(in srgb, var(--surface) 95%, var(--bg));
    border: 1px solid #eee;
    border-radius: var(--border-radius-sm);
    margin-bottom: 0.8rem;
    padding: var(--spacing-sm);
    align-items: center;
    gap: var(--spacing-sm);
}

.timetable-entry .time {
    font-weight: 600;
    color: var(--brand-secondary);
    width: 80px;
    flex-shrink: 0;
}

.timetable-entry .details {
    flex-grow: 1;
}

.timetable-entry .details strong {
    color: var(--brand-primary);
}

/* Loading Skeleton */
.loading-skeleton {
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: loading 1.5s infinite;
    border-radius: 4px;
    height: 1.2em; /* Adjust height based on text line-height */
    margin-bottom: 0.5em;
    display: block;
    width: 100%;
}

.loading-skeleton.short {
    width: 60%;
}

.loading-skeleton.medium {
    width: 80%;
}

.loading-skeleton.long {
    width: 100%;
}

table .loading-skeleton {
    height: 20px;
    margin-bottom: 0;
    width: 95%; /* Adjust for table cells */
}

ul .loading-skeleton {
    height: 1.2em;
    margin-bottom: 0.5em;
}

@keyframes loading {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

@media (max-width: 768px) {
    header {
        flex-direction: column;
        gap: var(--spacing-sm);
        padding: var(--spacing-sm);
    }

    nav {
        flex-direction: column;
        gap: var(--spacing-xs);
        width: 100%;
        text-align: center;
    }

    nav a {
        width: calc(100% - 2rem);
    }

    .container {
        padding: 0 var(--spacing-sm);
    }

    .grid-container {
        grid-template-columns: 1fr;
    }
}